Physics-Based Earthquake Simulations in Slow-Moving Faults: A Case Study From the Eastern Betic Shear Zone (SE Iberian Peninsula)

In regions with slow-moving faults, the incompleteness of earthquake and fault data complicates the study of seismic hazard. The instrumental and historical seismic catalogs cover a short period compared with the long-time interval between major events. Paleoseismic evidence allows us to increase the time frame of actual observations, but data is still scarce and imprecise. Physics-based earthquake simulations overcome the limitations of actual earthquake catalogs and generate long-term synthetic seismicity. The RSQSim earthquake simulator used in our study reproduces the earthquake physical processes based on a 3D fault model that contains the kinematics, the long-term slip rates and the rate-and-state friction properties of the main seismogenic sources of a region. The application of earthquake simulations to the Eastern Betic Shear Zone, a slow fault system at southeastern Spain, allows the compilation of 100 kyr-synthetic catalogs of MW > 4.0 events. Multisection earthquakes and complete ruptures of some faults in this region, preferentially on strike-slip dominant ruptures, are possible according to our simulations. The largest MW > 6.5 events are likely as a result of jumping ruptures between the Carboneras and the Palomares faults, with recurrence times of < 20,000 years; and less frequently between the Alhama de Murcia and the Los Tollos faults. A great variability of interevent times is observed between successive synthetic seismic cycles, in addition to the occurrence of complex co-ruptures between faults. Consequently, the occurrence of larger earthquakes, even MW ≥ 7.0, cannot be ruled out, contrasting with the low to moderate magnitudes recorded in the instrumental and historical earthquake catalog

Earthquake geology of shallow crustal faults and Seismic Hazard Assessment: Challenges ahead

With the development of modern techniques, we are able to improve the mapping of faint coseismic or cumulative surface deformation features, potentially enabling detection of blind faults. This also opens the opportunity to improve the empirical relationships relating earthquake magnitude to coseismic surface displacement or fault length towards the moderate magnitudes. The developing use of the probabilistic approach in assessing the surface displacement threat requires enhanced catalogues with both primary and distributed rupture evidences, to feed the attenuation relationships of displacement with distance. Another key point is to include the local conditions, including surficial geology, soil parameters and crustal rheolog